Microelectromechanical system (MEMS) devices typically include at least one freely movable structure within a recess formed in a substrate and covered by a “lid” or overlying layer. Often the lid includes openings therethrough to allow etchant to be employed in removing a sacrificial material fixing the movable structure in place until the enclosure surrounding the structure is completely formed. Such openings, if not too large, may be subsequently sealed by sputtering metal into the opening. However, openings through the lid that are too small may not allow sufficient etchant to pass through to etch the structure as desired. Accordingly, the size of the openings and/or the time required to perform an etch through the openings is constrained.
In addition, if the area that must be covered by an unsupported portion of the lid is too large, the lid becomes fragile or prone to deformation, fracture or breakage. In a worst case, problems with the lid may potentially interfere with free movement of MEMS device structure. A large number of small openings through the lid merely increases the fragility of the lid.
There is, therefore, a need in the art for an improved lid for MEMS device structures.